Loose objects carried in a pickup truck box can shift toward the front of the truck box and be projected through the rear window of the truck cab when the pickup truck comes to a sudden stop or decelerates quickly. It is therefore desirable to protect the rear cab window, and the passengers of a pickup truck, from such loose objects carried in the truck box A cab guard is also advantageous for protecting the cab window from damage due to careless handling of long objects in and out of the truck box.
Pickup trucks have different dimensions from one model to another and from one year of manufacture to another in a same model. Therefore, most cab guards used in the past were custom made by the truck owners to fit their own trucks. Few manufacturers have introduced cab guards to be sold as after-market accessories. However, these cab guards are also limited as to the models of pickup trucks on which they can be mounted.
Examples of cab guards of the prior art being sold as after-market accessories are described in the following documents:    U.S. Pat. No. 4,611,824 issued to Thomas K. McIntosh on Sep. 16, 1986;    U.S. Pat. No. 4,867,497 issued to Gilbert Jayne on Sep. 19, 1989.
Although the prior art cab guards deserve undeniable merits, it is believed that a need still exists for an universal cab guard that can be fitted to most North American pickup trucks now in service, without modification to the truck itself.